Can you see any differences between these millimeter-long male and female ostracodes (tiny ocean animals)? Microscope photos of fossil ostracodes.
(Bottom, left) In this species of tiny animal called an ostracod, males are smaller than females and have special light organs that they use to compete for females by emitting flashes of bioluminesence. (Gene Hunt, Smithsonian/Jim G. Morin)

In the animal kingdom, sexual reproduction is the rule. This is even true for tiny ocean animals. One example is ostracodes. With just a few exceptions to the rule, male sex cells must fertilize female sex cells. That is how they make offspring. Some animals, such as male and female clams, release sex cells into the water for chance encounters. But reproduction in many animals requires that males and females find each other.

Attracting individuals of the same species is achieved in a startling variety of ways. They can make creative use of the senses. This activity can range from singing by frogs to dancing by jumping spiders to luminescing by deep-sea animals. Once found, a potential mate may need to be convinced to go forward with the mating relationship. Generally, it's the male doing the convincing. This is because females usually make the larger investment in creating and raising offspring. So females are choosier about who to mate with.

Let's take birds as an example. In birds, males invite females to their territories by singing, sporting bright feathers and doing courtship dances. The more flamboyant males tend to be more successful at attracting females. This activity by males drives a sort of evolutionary arms race. Which one can have the showiest feather plumage? Showier plumage may lead to more mating opportunities. This leads to more offspring. That perpetuates showier plumage in the population of birds.

This form of natural selection driven by mate choice is called "sexual selection." While it has inspired spectacular characteristics in animals, from feathers to antlers to lion manes, it might have a dark side. Peacocks with larger tails may be easier for wild dogs to catch, for example. Elks with larger antlers might not be as agile against wolf attacks. And a lit-up squid might attract a hungry fish instead of a mate. Species with more extreme differences between males and females ("sexual dimorphism") might be more susceptible to extinction in the long run.

Smithsonian paleontologist Dr. Gene Hunt is using tiny ocean ostracodes as a model to examine a hypothesis. It is that sexual selection plays a role in extinction. Learn more about what his studies of ostracodes are revealing in a live "Smithsonian Science How" webcast. It airs on Thursday, Feb. 9. In "What Tiny Marine Fossils Reveal about Extinction" (airs at 11 a.m. and 2 p.m. EST on the Q?rius website), Gene will show you how he tests hypotheses. He also will answer your questions live. You can also get teaching resources to use with the webcast.

This article discusses sexual selection and how it might affect survival of a species. They are questioning whether or not sexual selection will positively affect the ability to keep a species going.

I personally think sexual selection is very important to survival of a species. The better a species can select good mates, the stronger their species will be. The stronger their species, the better the survive.

hemyp-har

2/07/2017 - 02:50 p.m.

Species with more extreme differences between males and females may be more susceptible to extinction because in the process of trying to mate they are attracting other animals. These other animals may think they look good and eat them. The males are more likely to get eaten due to the fact that they are the ones trying to impress. the females are not. The males are trying to impress with their large feathers, songs, dances, etc.

handroh-ver

2/10/2017 - 10:03 a.m.

this is weird because they're saying that they can become extinct is the males don't try harder to mate with females to produce.

jennac-ver

2/10/2017 - 12:06 p.m.

They are saying that if the animal species don't have anything in common they won't eat to reproduce. And the males to try harder to mate with the females and then they don't reproduce as much. Also I think it's is cool how birds sing and do a dance to get the female to go by them.

henriettaw-ver

2/10/2017 - 12:14 p.m.

If other animals can mate why can't oysters?

allisons-kul

2/13/2017 - 01:56 p.m.

Oysters can obviously mate otherwise they'd become instinct. In the article, it says they release male and female reproduction parts in the water and hopefully they meet up. Oysters just don't mate the way other animals do.

kayleeb-kul

2/16/2017 - 12:25 p.m.

Oysters are actually hermaphrodites and are able to fertilize their own eggs. They don't technically need a mate as they are able to change their sex. Oysters are definitely a strange creature.

jaquism-mac

2/10/2017 - 12:39 p.m.

it would be more susceptible to extinction because if the females have no protection and the males do the female extinction will go down.

monad-mac

2/10/2017 - 01:20 p.m.

Maybe they have simliar things in common,but not alot of things can mate together.

zaneh-jon

2/12/2017 - 09:25 a.m.

The article's topic is rather interesting but I was expecting more about the topic than there actually is. However, it is nice to learn about animal mating and I'd like to hear more on how it affects extinction.